On Saturdays, the doctor is available only in the mornings.
The consultation hours for Saturdays are for mornings only.
The hospital is open on Saturdays, but only in the mornings.
ご質問ありがとうございます。
① "On Saturdays, the doctor is available only in the mornings."＝「土曜日は、午前中しか医師はいません。」
② "The consultation hours for Saturdays are for mornings only."＝「土曜日の診療時間は午前中のみです。」
③ "The hospital is open on Saturdays, but only in the mornings."=「病院は土曜日に開いています、でも午前中だけです。」
ご参考に。
アメリカ合衆国 
